Geochemical evolution and mechanisms controlling groundwater chemistry in the transboundary Komadugu–Yobe Basin, Lake Chad region: An integrated approach of chemometric analysis and geochemical modeling
Abdulrahman Shuaibu, Robert M. Kalin, Vernon R. Phoenix, Ibrahim Mohammed Lawal
Abstract
The study is conducted in the transboundary Komadugu–Yobe Basin, Lake Chad region, a critical groundwater resource shared across national boundaries of Nigeria and Niger Republic. The research investigates geochemical evolution and sources of chemical constituents in groundwater through an integrated methodology that integrates geochemical modeling, molar ratios, bivariate plots, and chemometric analysis. Groundwater samples (n = 240) were collected during wet and dry seasons to identify seasonal variations and the impact of geogenic and anthropogenic processes on groundwater quality. The findings revealed that Cl⁻ and NO₃⁻ are associated with anthropogenic pollution. The Principal Component Analysis identified three main components associated with geogenic and anthropogenic processes, agricultural pollution, and mineral weathering. Hierarchical Cluster Analysis highlighted geogenic, anthropogenic, and evaporative influences. Groundwater in the basin is predominantly of Ca–HCO₃ and Na–Cl types and is significantly undersaturated with calcite, dolomite, and fluorite, though seasonal variations show saturation in some samples. Elevated partial pressures of CO₂ (pCO₂) above atmospheric pCO₂ in nearly all samples suggests active biogeochemical processes. Moreover, Gibbs plots, molar ratios, and bivariate plots, along with chloroalkaline indices (CAI-I & CAI-II) confirms influence of mineral weathering and ion exchange reactions within the aquifer system. Few locations show evaporation during the dry season. This study provides valuable insights for sustainable management of groundwater resources in semi-arid and arid regions. • Chemometric analysis is essential in assessment of groundwater geochemistry. • Groundwater geochemistry is defined by geogenic and anthropogenic processes. • Gibbs diagrams, molar ratios, and chloroalkaline indices reveal mineral weathering and ion exchange in aquifer systems.